GWEN IFILL: Next, today is World Water Day.
Tonight, we look at an innovative approach to getting clean water to slum dwellers in so-called megacities.
Our story is another in our occasional reports about population issues around the globe. It's part of a collaboration with "National Geographic" magazine and the Pulitzer Center on Crisis Reporting and comes from special correspondent Steve Sapienza in Bangladesh.
STEVE SAPIENZA: Dhaka, the capital of Bangladesh, is one of the world's fastest-growing cities and one of the poorest. As in many other developing countries, people are leaving the countryside in search of work and a better life in the city. Dhaka's population, now estimated at 15 million, is expected to hit 20 million by 2025.
DR. KHAIRUL ISLAM, WaterAid: Dhaka is one of the megacities which is growing too, too fast.
STEVE SAPIENZA: Country director for the charity WaterAid, Dr. Khairul Islam, says the increased population density is severely taxing the city's ability to house and care for its people.
KHAIRUL ISLAM: Almost 5,000 slums are in and around Dhaka City. And almost one-third of the population are living in -- at the low-income communities and slum areas. Most of them don't have ownership over those pieces of land that they're residing. But the main challenge is provisioning essential services for this huge number of population, mainly water and sanitation.
STEVE SAPIENZA: With 2,000 newcomers daily, the struggle to find clean water in the slums often has life-threatening consequences.
MAN (through translator): Water? Yes, we have water, but the water is not always available. When water is available, it is often bad. Yesterday, a woman here thought she had cholera. She went to the hospital, but she died last night.
STEVE SAPIENZA: If you want to see the human toll exacted by unsafe water and poor sanitation in Dhaka, you come here. This is the overflow tent at the short-stay unit at Dhaka's main cholera and diarrhea hospital.
This man arrived at the hospital with no vital signs. After 15 minutes of trying to revive him, his wife is given the news. The staff reports cholera as the cause of death. The hospital's lead research scientist, Dr. S.K. Roy, and his colleagues work around the clock 365 days a year to save lives threatened by waterborne illness. The majority of the patients here are the urban poor, and the hospital care is free.
DR. S.K. ROY, International Center for Diarrheal Disease Research: We are now having about 400 patients every day. But in August, September, sometimes we go up to 1,200 a day. Then I can tell you, the average of a year is 120,000 patients every -- in a year. So, this hospital is a quite busy one, most of them having E. coli diarrhea and cholera diarrhea. Then we are having (INAUDIBLE) patients, quite a high number. So, these are coming through water and via hand contaminations.
STEVE SAPIENZA: Most diarrhea patients are released within 12 to 24 hours of receiving treatment. But at a nearby clinic, two newcomers to Dhaka have been battling the illness for five days.
Fezila Begam believes her baby, Saim, became ill after drinking water from a shared well. When the baby is finally cleared to leave, the attending doctor warns Fezila the Saim is in precarious shape and needs safe drinking water, regular meals and rest.
Fezila rents a small room at a nearby slum for $20 a month. She shares cooking, water and toilet facilities with 25 neighbors. Neighbors say the shared well provided by the landlord is not deep enough to avoid contamination. Many here complain of frequent dysentery, and the evidence, small packs of saline rehydration solution, is everywhere.
Fezila knows the conditions are unsafe, but she already pays more than she can afford to live here.
WOMAN (through translator): I know it's not a good situation, but what am I supposed to do?
STEVE SAPIENZA: The job of supplying safe water to residents belongs to the Dhaka Water and Sewage Authority, DWASA for short. Residents need city approval before they can extract water or connect to city water pipes. But approval to use city water is only given to residents who can provide proof of land ownership. This leaves four million slum dwellers without legal access to city water.
With few options, they end up paying high prices for suspect water supplied by slumlords, or they buy costly bottled water from the roving carts of water sharks. Still others tap illegally into city water pipes.
DR. DIBALOK SINGHA, Dushtha Shasthya Kendra: DWASA was with the system that was tied with house ownership. That actually forced us to talk with Dhaka WASA that, why it is not possible to provide water to slum dwellers?
STEVE SAPIENZA: Dibalok Singha lobbied the city to give a water license to his startup NGO on behalf of slum communities.
DR. DIBALOK SINGHA: They explained at that time that they are giving water only to people who have their own houses. So, we tried to facilitate that service to slums, linking them the Dhaka Water and Sewage Authority.
STEVE SAPIENZA: Linking slums to city water service has meant Dibalok's NGO assumed the risk if the slum dwellers failed to play the water bills. But Dibalok knew the slum dwellers, who pay 15 times the DWASA rate for water on the black market, would pay their bills.
DR. DIBALOK SINGHA: A win-win situation actually occurred, because Dhaka WASA, they wanted their revenues. On the other hand, poor people, they want the service. And they immediately see the economic advantage of getting access to Dhaka WASA water supply, because that is cheap, in comparison to private market. So in that way, it started.
STEVE SAPIENZA: NGO-backed water access points, like this one, are now sprouting up in the slums all over Dhaka.
Each community forms a water committee that pays to install the pump and for the costs of operation and maintenance. These committees also collect and pay the water bills. The success of earlier NGO-backed water points now enables community groups in slums to negotiate directly with the city for legal water access without NGO help.
DR. DIBALOK SINGHA: Anybody living in urban slums, they can apply for the service. And if they are willing to pay for the service, DWASA has no problem.
STEVE SAPIENZA: Today, there are over 1,000 water connections in 100 slums. But that leaves some 5,000 slums with no such service.
DR. DIBALOK SINGHA: Still, today, there are slums and squatters where these services are not available.
STEVE SAPIENZA: With new residents like Fezila and Saim arriving every week, the need for more city-to-slum water connections will remain urgent.
GWEN IFILL: Steve's report was a partnership with the Pulitzer Center on Crisis Reporting.
For more on the population project, follow a link on our website at NewsHour.PBS.org.